Power-transmission mechanism



w. B. MOSES.

POWER TRANSMISSION MECHANISM.

APPLICATION FILED FEB. 23. I917.

1,347, 1 17. I Patented July 20, 1920.

UNITED STATES PATENT OFFICE.

WILLIAM B. MOSES, OF BROOKLINE, MASSACHUSETTS, ASSIGNOR TO GRAY & DAVIS,

INCORPORATED, OF CAMBRIDGE, MASSACHUSETTS, A CORPORATION OF MASSA- CHUSETTS.

rownn-rmnsmssron MECHANISM.

Specification of Letters Patent.

Patented July 20, 1920.

Application filed February 23. 1917. Serial No. 150.294.

bustion engine to start the latter, and is automatically disconnected when the engine operates under its own power.

Among the various automatic coupling and uncoupling devices which have been used for this purpose in engine starters there A is the interiorly threaded pinion mounted on the motor shaft which is correspondingly threaded, and it is to this type of automatic coupling that the invention particularly relates. The interiorly threaded pinion which constitutes the driving member when in action is caused tomove longitudinally on the shaft by the rotation of the threaded shaft within the pinion, the pinion being held or retarded against rotation with the shaft by its own inertia or by being unbalanced. Difiiculties have arisen in connection with the use of apparatus of this type in that accidental movement of the motor shaft or of the pinion on the threaded shaft, due to vibration or other causes, sometimes causes the pinion to move along the shaft and come into contact with the teeth of the gear driven by the pinion. This has sometimes resulted inthe breaking of the teeth of one or both of the intermeshing members, and has also resulted in objectionable noise. Oneiof the principal objects of the invention is to prevent such accidental movement of the driving pinion into contact with the driven member.

In the accompanying drawings which illustrate one embodiment of the invention,-

Figure 1 is a side elevation of an engine starter containing the invention, parts being broken away;

Fi 2 is an enlarged side elevation showing t e coupling device; and

Fig. 3 is a plan view of Fig. 2. The crank shaft of an internal combustion engine is shown at 1, having fixed thereon a sprocket wheel 2 adapted to receive asilent chain 3, which connects the sprocket wheel 2 with a somewhat smaller sprocket. wheel 4 on a countershaft 5: "In the embodiment shown the counter shaft 5 is an extension of the armatureshaft of a generator unit 6. T-here is also mounted on crank shaft 1 a pulley 7, which is connected by belt 8 with a fan pulley 9 fixed to the fan 10 for cooling the engine.

On the armature shaft 5 of the generator there is also fixed a large spur gear 11 which constitutes the driven member ofthe automatic coupling and uncoupling. device. 12

is an electric starting motor, both the motorj 12 and the generator 61being preferably mounted upon the same bracket 13 which-is in turn supported on the engine. The motor 12 has its armature shaft 13' extended toward the left as viewed in the drawings.

and on its extreme end is pinned a collar 14. A sleeve or hollow shaft 15 is mounted on the shaft 13 inside of the collar 14, and the collar 14 and sleeve 15 are connected together by means of acoil spring 16 which has one end secured around the shank of a bolt 17 and the other secured around the shank of the bolt 18. The bolt 17 serves both to hold the end of the spring lfi relatively to the collar 14, and to hold the collar 14 in place on the shaft 13', The spring 16 constitutes a yielding connection between the sleeve 15 and the armature shaft 13' of the motor. 1.

The sleeve or hollow shaft 15 has a reduced and threaded portion 21, and at its right hand extremity a collar22 is fixed to the sleeve, serving as a stop to limit the longitudinal travel in that direction of the pin ion 23. The pinion 23, interiorly threaded to correspond to the threads 21, is loose on the threaded sleeve or shaft 21, and as the threaded sleeve 21 turns within the-pinion the latter is caused to travel lengthwise. The longitudinal travel of the pinion toward the left is limited by the shoulder 24 between the unthreaded and the reduced threaded portion of the sleeve. The pinion 23 has a flange 25, a part of which is cut pinion and thereby aid in holding the pinion against rotation as the motor shaft and threaded sleeve 21 turn therein.

Secured to the bolt 18 between the head of the bolt and washer 19 is a spring strip 20 suitably held against movement about the shank of the bolt 18. ()n the spring 20 there is formed a projection 27 which normally lies in the path of travel of the flange 25 of the threaded pinion 23. Near the free end of the spring strip 20 is secured a weight 28 to increase the effect of the centrifugal force of rotation on the spring strip 20. a

The operation of the device is as follows: Assuming that the engine is at restand the operator desires to start the engine, the

electric motor is energized through suitable connections 'to a storage battery (not shown), whereupon the motor shaft 13 is rotated at comparatively high speed and the rotary motion is imparted to the threaded sleeve through collar 14 and coil spring 16. The pinion 23, owing to its own inertia aided by the fact that it is unbalanced, will not rotate with the threaded sleeve 21 but is caused to move longitudi-.

nally toward the right as the threads 21 turn therein, until its teeth have fully meshed with the teeth of spur gear 11. This longitudinal movement will continue until the pinion meets and is stopped by the collar 22, whereupon no further. longitudinalmovement being possible the pinion will turn with the sleeve and motor shaftand act as a driving member to rotate gear 11. From gear 11 the power is transmitted through the chain and sprocket mechanism to the crank shaft 1 of the. engine.

Vhen the motor is energized and the motor shaft 13' is rotated, the centrifugal force of rotation acting upon the spring that imparted to the gear 11 by the motor 12. In consequence, the pinion 23 will overrun or exceed the speed of rotation of the threaded sleeve 21, whereupon the pinion is caused to move longitudinally in the opposite direction, or toward the left, on the threaded sleeve 21. The increase in speed of rotation of the gear 11 and consequently of the pinion 23 is so great and takes place so quickly, that the pinion is forced out ofmesh suddenly and with, such force that it continues its longitudinalmovement to- 23 out of mesh with the gear 11, the operator releases the motor starting switch, thereby denergizing the motor, which comes to rest, and the spring strip 20 again assumes its normal position with the stop 27 in the path of the flange 25. The stop 27 will now prevent the movement of the pinion 23 toward the right due to vibration or other accidental causes until such time I as the motor is again operated, when spring strip 20 is again swung outwardly by the centrifugal force of rotation.

As the spring stop .27 is supported independently of the pinion and is normally out of contact therewith, there is nothing to cause the pinion to rotate with themotor shaft when the motor is started up and so prevent its traveling longitudinally on the threaded sleeve into mesh withthe gear 11.

The above described construction insures the holding of the two separable coupling or transmission members 23 and 11 out of engagement except upon the starting of the motor 12 when it is intended that the two should be meshed. The possibility of grating or breaking the teeth of the two members, as well as the objectionable noise caused by their engagement, when the engine is running under its own power, are eliminated.

I claim:

1. Apparatus of the character described, comprising a driven member, a driving member normally disengaged from the driven member, a motor, rotary means actuated by the motor to causethe engagement of the driving and driven members, and a stop carried by said rotary means adapted to prevent accidental engagement of said members when the motor is not running,'and adapted to be moved to inoperative position by centrifugal force when the motor is running. j

2. Apparatus of the character described, comprising a driven member, a driving member normally disengaged from the driven member, a motor, rotary means actuated by themotor to cause the engagement of the driving and driven members, and a spring stop carried by said rotary means normally in the path of travel of the driving member adapted to prevent accidental engagement of said members when the motor is not running, but movable under the influence of centrifugal force out of the path of travel of the driving member when the motor is running.

,3. Apparatus of the character described, comprising a motor, a threaded shaft rotated thereby, a driving pinion loosely threaded on said shaft, and a yielding stop carried by said'shaft adapted to restrict lon gitudinal movement of the pinion on the shaft when the latter is not running, and movable under the influence of centrifugal force to permit longitudinal movement of the pinion on the shaft when the latter is running.

4. Apparatus of the character described, comprising a motor, a threaded shaft rotated thereby, a driving pinion loosely threaded on said shaft, and a weighted spring arm carried by said shaft having a stop normally in the path of travel of the driving pinionadapted to restrict longitudinal movement of the pinion on the shaft when the shaft is not running, and movable under the influence of centrifugal force to permit such longitudinal movement of the pinion when the shaft is running.

Signed by me at Boston, Massachusetts, this 20th day of February, 1917.

WILLIAM B. MOSES. 

